Electric furnace



Oct. 22, 1963 R. J. GARMY ETAL 4 3,108,l5l

.ELECTRIC FURNACE BY E a/14 s E. Psem R. J. GARMY ETAL ELECTRIC FURNACE 15 Sheets-Sheet 3 Filed Jan. 16, 1959 INVENTORS ?034-727 JT mue/W BY o/ma E. ?Ez/ey x. N %mu Oct. 22, 1963 R. J. GARMY ETAL ELECTRIC FURNACE 15 Sheets-Sheet 5 Filed Jan. 16, 1959 0ct.'22, 1963 R. J. GARMY ETAL 3108151 ELECTRIC FURNACE Filed Jan. 16. 1959 15 She ets-Sheet 6.

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- INVENTORS BY mom: i IDE/?KV Oct. 22, 1963 R. J. GARMY ETAL ELECTRIC FURNACE 15 Sheets-Sheet 7 Filed Jan. 16, 1959 llll Il l INVENTORS fiosszr J. mew BY mam.: f. &ve/ey Arra/av Oct. 22, 1963 R. J. GARMY ETAL 3,l08,151

ELECTRIC FURNACE Filed Jan. e, 1959 s sheats-sheet s TTlE INVENTORS ?03527 J 64 944/ BY 7740/1445 E, EPEV Oct. 22, 1963 R. J. GARMY ETAL &103,151

- ELECTRIC FURNACE' Filed Jan. 16, 1959 15 Sheets-Sheet 9 iii?- INVENTORS ,905527 J xew BY 77-/ M s f, Pie/ey %MZ ATTOZA/E Oct. 22, 1963 R. J. GARMY ETAL ELECTRIC FURNACE 15 Sheets-Sheet Il Filed Jan. 16, 1959 EFTI a .MP. M MJ: m MS M emm JA/.M

Oct. 22, 1963 R. J. GARMY ETAL ELEC'I'RIC FURNACE 15 Sheets-Shet 12 Filed Jan. 16, 1959 TSTEI.

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INVENTOR5 ROBERT J AEMV Oct. 22, 1963 Fileddan. 16, 1959 ll IIH Il R. J. GARMY ETAL 3,108,l51

ELECTRIC FURNACE 15 Sheets-Sheet 13 INVENTOR5 ROBERT J AEMV BY T m/WAS f, PEERV ArmkA/ V Oct. 22, 1963 R. J. GARMY ETAL ELECTRIC FURNACE Filed Jan. 16, 1959 15 Sheets-Sheet 14 H TAHF. m m V JE m Z m m Oct. 22, 1963 R.J. GARMY ETAL ELECTRIC FURNACE INVENTORS Pos/Fer J AIe/W [4732245 Pfffiy United States Parent O %183,151 ELECTHC FURNACE Robert J. Garrny, Cantou, and Thomas E. Perry, North Canton, Ohio, aasignors to Republic Steel Corporation,

ieveiand, Ohio, a corporatien of New .iersey Fied an. te, 1959, Ser. No. 7873266 6 Claims. (CE. 13-10) The present invention relates to a method and apparatus for forming ingots. This method and apparatus were devised particularly tor use in connection with titanium and other similar meltable materials which have i high melting points and a Chemical afiinty for an atmosphenic gas, such as oxygen, when heated to the neighborhood of their meltin g point. I-Iowever, the method and apparatus described are not necessarily limited to use with such materials, but may be used to advantage with other materials, e.g.,tsteel, whenever an ingot of high purity is desired.

The prior art methods of making titanium have been adapted to use as raw materialseither titanium sponge, as in the apparatus disclosed in U.S. Patent No. 2,800,- 519, issued to Robert J. Garmy on July 23, 1957, or to use consumable electrodes formed of compressed sponge, as in the apparatus described in the copending application of Robert J. Garmy, Serial No. 698356, filed November 22, 1957, now Patent No. 2,973,452. The adaptability of such apparatus to the use of scrap titan-ium is limited. In fact, so far as is known, there has been no practical process, prior to the present one, which was adaptable to the use, as a raw material constituting the entire initial charge, of scrap titanium in all of the many forms in which scrap is produced industrially. This lack of ability to utilize scrap has kept the prices of titanium and other such materials at high levels, and has limited their adaptation to many commercial uses.

An object of the present invention is to provide a method and apparatus `for forming ingots ,of titanium and the like which is capable of using as a raw material titanium scrap in practically any form.

Another object is to provide an improved method of melting scrap metal, which method is adaptable for use with difficultly meltable metals such as titanium, zirconium and the like.

Another limitation ofthe prior art methods and apparatus for producing ingots of titanium and the like has been that only a small amount of material being melted was maintained molten at any given time. Typically, the ingot was built up in a vertically `extending generaliy cylindrical crucible, raw material being added at the top of the cru'cible throughout the ingot forming process. The rate of addition of raw material and the rate' of heat supply were controlled so that only a small portion of the material in the -crucible was liqui-d at any time. As the ingot built up in the crucible, it consisted of a solid ingot with a pool of molten material on its top, to which materiai being melted was continually added, and from which material was continually solidifying at the bottom of the v pool.

genetity of the ingot.

Another object of the present invention is to provide a method and apparatus for forming ingots of materials of the type described, 'in' which the material tor the eni convenient form, either sponge or scrap.

3,198& 5 1 Patented Oct. 22, l 963 tire ingot body is maintained molten and is poured in a molten state into a mold.

Another object is to provide a method and apparatus of the type described, which is capable of holding in a molten state a quantity of metal sutiicient to cast a sizable object in a shape or form other than a cylindrical ingot.

A further limitation of the prior art methods and apparatus cfor formirg ingots from titanium and the like is that the superheat of the titanum was limited and also was not closely controllabie. By superheat is meant the difference between the melting point of titanum and the higher temperature at which it is maintained in the furnace.

The previous furnaces were limited in the metallurgcal results they could pro duice in their ingots by reason of their inability to reach high superheat te-mperatnres and to 'control those temperatures accurately.

A further object of the invention is to provide 'an improve-:l method and apparatus for forming ingots of titanium and the like, in which a meitable material may be maintained, in substantal Volume, at temperatures considerably above its melting point, just prior to pouring.

lt has been proposed to construct -urnaces for the melting of titanium and the like, which have been termed "skuli furnaces from the fact that the crucible in which the material was melted utilized as a liner, a thick, hollow, hemispherical layer of material being melted. Such a layer is referred to as a "skull" Commonly, the skulls in the prior art furnaces have been rather thin (about 1" thick), and no attempt has been made to control the skull thickness during the melting operation. In the previous methods and apparatus using skulls, the crucible has been formed of refractory material or the like, having low thermal conductivity.

Another object of the present invention is to provide a skull furnace in which the thiclcness of the skull may be controlled during the melting operation. A further object is to provide a skull furnace of the type described in which the skull thickness is controlled by using a cooled coppier shell for the oruoible, and 'balancing the heat input through the are against the heat extracted through the shell.

The foregoing and other objects of the invention are attained in the method and apparatus described herein. Typically, the apparatus comprises a crucible located inside a sealed enclosure. Means is provided for evacuating the en ciosure. The crucible is tiltable so that material melted in it may be poured :from it into one or more `molds which are also located inside the enclosure. For the purpose of changing the crucib le, the enclosure may be opened and the crueible 'loaded with titanium in a The enclosurc is then closed and `evac-uated and an arc is struck between a consumable electrode and the material in the crucible. The consumable electrode :continues to add material to the crucble as long as its are is maintained, and is efec tive to melt down the material in the crucible.

The crucible comprises an outer shell of Copper or other material having high thermal conductivity, and a skull of the material being melted, which skull is built up and maintained at the inner surface of the shell, by the use of cooling means on the outside of the shell. The skull must have an appreciable thickness and be strong enough to contain the melt. The melting with the consumable electrode continues until all the material originally supplied and that added by the consumable electrode has been melted into a large unitary mass which fills the crucible to a desired level. The arc from the consumable electrode is then extinguished and it is withdrawn. In its place a plurality of non-consumable electrodes are moved into arcing relationship with the surface of the liquid mass. The power supplied to these electrodes is controlled to determine the temperatures developed in the mass of the material. Theiheat loss from the outside of the mass of material through the solid skull and the shell is controlled by controlling the temperature of the coolant (a certain amount of heat is also lost by radiation from the liquid surface), and the heat supplied to the mass is determined by the power supplied through the non-consumable electrodes. The equilibrium temperature and thus the degree of superheat maintained in the mass, and the thickness of the skull, may be readily controlled by so controlling the heat supply and heat loss.

In order to prevent contamination of the ingot and to refine the melt by the extraction of hydrogen, it is highly desirable to maintain a high vacuum in the furnace. From the standpoint of purity, the vacuurn should be somewhat higher than that which produces the best arc characteristics. In order to enable the use of such high vacuum without adversely affecting are characteristics, the non-consumable electrodes are made hollow and a continuous supply of `an inert gas, e.g., a mixture of argcn and helium, is supplied through the hollow electrodes so that the pressure conditions in the immediate neighborhood of the arc are raised somewhat above the highly evacuated conditions elsewhere in the furnace.

In order that the molten material in the crucible may be thoroughly mixed, there is provided a coil encircling the outside of the crucible, which is supplied with direct electric current suflicient to establish a vertically extending magnetic field throughout the crucible; This field reacts with the Currents fiowiug through the molteu material in the crucible so as to stir that material continuously in one direction, thereby keeping it well mixed while preventing the formation of eddies or the like which might result in the formation of stationary portions of the material.

After the material has been brought to a desired degree p of superheat and maintained there for a desired length of time, the material in the crucible is poured into a mold or molds located within the enclosure. 'The pouring is accomplished by withdrawing the non-consumable electrodes and tilting the crucible'so that the material therein pours over a suitably -formed'pouring spout or lip into the mold. The fulcrum about which the crucible tilts is preferably located near the spout so that the path of the pouring stream remains n-early the same throughout the pour;

Other objects and advantagesof the invention will become apparent from a consideration of the following specification and claims, taken together with the accompanying drawings.

In the drawings:

FIG. 1 is a vertical sectional View of an ingot forming furnace embodying the invention, taken on the line I-I of FIG. 3;

FIG. 2 is a cross-sectional view taken on the line H-H of -FIGS. 1 and 3, showing the main enclosure of the furnace in FIG. 1 and certain auxiliary apparatus located below the main furnace and not included in FIG. l; i

FIG. 3 is a horizontal sectional view of the furnace of FG. 1, taken on the line lil-HI of FlGS. 1 and 2;

FIG. 4 is a vertical sectional view of one of the nonconsumable electrodes in the furnace of FIGS. 1 to 3;

FIGS. 5 to 11 show diagrarnmatically, successive steps in the process of forming and ingot using the furnace of FIGS. 1 to 4;

FIG. 12 is an overall front elevational view of a modified form of furnace embodying the invention, with certain parts omitted for clarity;

FIG. 13 is an overall side elevational View of the furnace of FIG. 12, with certain parts omitted for clarity;

FlG. 14 is an enlarged elevational view of the enclosure of the furnac-e of FIG. 12 with certain parts broken 4 away and others shown in section to illustrate the internal pats;

Fl'G. 15 is a view similar to MG. 13, somewhat enlarged and showing only the main enclosure of the furnace and with certain parts broken away and others shown in section;

FIG. 16 is a sectional View taken along the line XVI-XVI of FIGS. 12 and 13;

FIG. 17 is a view of the crucible and its supporting structures taken from the rear as they appear in FIG. 14, and substantally enlarged;

EFIG. 18 is a plan View of the crucible of FIG. 17;

FIG. 19 is a left side elevational View of the crucible of FIG. 17; i

FIG. 20 is a right side elevational view of the crucible of FIG. 17;

FlG. 21 is a fragmentary View similar to a portion of FlG. l4, but somewhat enlarged;

FIG. 22 is a plan View of FIG. 21, showing the top of the furnace with certain parts removed;

-FIG. 23 is a vertical oross-sectional view of a modified form of non-consumable electrode which may be use in the turnace of FlGS. 14-22; i

FIG. 24 is a horizontal cross-sectional View, taken on the line XXIV-XXIV of FIG. 23;

FIG. 25 is a diagrammatc il-lustration of a coolant circulation system in the furnace of FIGS. 14-22; and

' drawn and the temperature of the melt ris further raised by the 'use of non-consumable electrodes.

FIGS. I to 4 There is shown in FIGS. 1 to 3, a furnace comprising an enclosure or cranlc 1 of generally circular horizontal cross-section. The enclosure 1 is provided with an out let connection '2, which is connected to a Vacuum pump, not shown, by means of which the pressure inside the enclosure 1 may be reduced to 'and maintained at a subatmospheric pressure. The enclosure 1 is provided with a cover plate 3. Projecting upwardly from the center of the cover plate 3 is an electnode tube 4 for receiviug a consumable elec-tr ode `5 of the material to be melted( The upper end of the electrode 5 is gripped by a holder shown diagrammatically at `6 and attached to the lower end of a lead screw 7 driven by a rotating nut `8 which is operatively connected, as shown diagrammatically in the drawing, to a motor 9.

The lead screw 77 is hollow, 'and water or other suitable l iquid coolant is circulated through itby means of hose connections 113 and a coupling lil. Electricity is conveyed to the electrode '5` by means of brushes 112 which engage the ends of the rotating nut 8 and which are connected through suitable `connectors to terminals 13 located on the outside of the electrode tube 4.

The lower end of the electrode 5 projects downwardly into a crucible 14, comprsing a cylindrical shell 1412, whose structural details may be similar to that shown in the copending application of Robert J. Garmy, Serial No. 651328, filed April `3, 1957, now P-atent No. 2,950,094, and a skull 54 within the shell. The crucible 14 has cooling jackets 15 and 16 on 'its bottom 'and sides, respectively, through which water or other suitable coolant i may flow. The crucible l lalso has a coil 17 for arc stabilizing and stirring purposes as shown and claimed in the copending application of Robert J. Garmy, Serial No. 671,154, filed July `ll, 1957, now abandoned. One side of the crucible M is provided on its upper end with a pouring spout 18 which be constructed of graphite.

The crucible 14 rests on a framework 19 supported on a plate 20 'of somewhat larger diameter than the framework 19 and adapted to engage at its edge a flange la which surrounds an 'opening in the bottom of the enclosure 1. The plate Zh rests, as best seen in -FTG, 2, on a platform .21. This platform 21 maybe raised or lowered by means of 'lead screws 22 mounted vertically in suitable hearing structures in a 'framework 23 carried by a truck 24 provided with axles 25 and wheels 26 tor movement along rails 27. A suitable motor (not shown) is provided for driving the -lead screws 22 concurrently.

'Inside the furnace enclosure 1 and above the cruoible 14 there are provided three non-consumable electrodes 28, the details of which are shown in FIG. 4. Referring to that figure, it may be seen that each electnode 28 comprises a tip 29, an internal ly threaded coupling member 30 and a power supply tube 31. The tip 29, which may be either of graphite or tungsten, is hollow .to provide a central passage 29'::. The upper end of the tip 29 is externally threaded to fit internal threads on one end of the couplin'g 34?. The coupling 3@ has a central aperture Sha aligned with the passage 2% and in fluid communication with it. A gas supply pipe 32 pnojects into the coupling 30 and has its lower end extendinig into the aperture 3961. Pipe 32 is concentric with the power tube 31. Another cylindrical tube 33 is concentric with the tube 31 and the gas supply tube 32 and lies between those two tubes. The tube 33 has its lower end terminating short of the bottom of the upper threaded recess in the coupling 30, so that coolant liquid may flow downwardly through the tube 33` and upwardly between the space between tube 33 and power tube 31. The lower end of tube 31 is externally threaded to engage the internal threads on the coupling 30.

The upper end of the tnbe 31 -s provided with coolant supply and drain couplings and with suitable current supp-ly couplings. These couplings are not shown in drawings, and may be generally similar to those shown in Garrny P-atent No. 2300519, mentioned above.

An auxiliary non-consumable :electrode 34 is provided, generally similar .in structure to the electrodes 28. The electrode 34 includes a power tube 35, which extends upwardly through the cover 3` and has its upper end attached to a carriage 36 supported by means of traveling nuts on a lead screw 37 driven by a motor 38. The electnodes 28 and power tubes 31 `are driven by similar motors and supporting mechanisms, which have been omitted from the drawing for the sake of clarity.

Within the enclosure 'i and aligned with the pouring spout 13, there is provided a turntable 3@ which supports a plurality of molds 48 and il. The mo'id ti) is generally similar in structure to the crucible 14, having water cooled sides and base to provide for rapid chilling of the molten material pour-ed into it. The molds 41 are of more conventional structure, being formed of graphite-or the like. Each mold may have a target plate 42, 43 in its bottom formed of the same material which is to be poured into it. The enclosure 1 is provided with access doors 44 on either side, by means of which access may be gained for removal of the molds iti and ti and the ingots poured therein. The upper side of the enclosure 1 's provided with a tube 45 closed at its outer end by a glass 46, through which the operation of the mechanism inside the enclosure may be observed. The entire enclosure 1 is m'ou nted in a thick walled chamber, 'one of whose wall-s is shown at 47 in FIG. 1. A heavy observation window 48 is provided in the wall 4-7. suitable control mechanism for the furnace is located outside the window 48. V

A hopper 49 (FIG. 2) is mounted within the enclosure v 1 on a pair of links 50, which permit it to be moved from the position shown in full lines in FIG. 2 to the dotted line position, where its inner end extends over the cruci-b'le 14. The hopper 49 may be fed with Supplementary scrap or sponge material through a Conduit 51 which extends through the upper side of the enclosure `l. 'suitable external means may be provided for feeding sponge into the conduit 51, such as that shown, for example, in Patent No. 2,8G0,S 19, mentioned above.

FIGS. 5 to 11 These figures illustrate diagrammatically the improved method for forming ingots using the apparatus of FlG-S. 1 to 4. The apparatus shown in these figures consists of a crucible 14 having a side wall water jacket 16 and a base water jacket 15.

The first melting run with a given crucible shell is utilized to form a skull which is used on later melting runs of material having the same composition,

For the first melt, there is placed in the bottom of the crucible shell a preformed slab 52 of titanium or other metal to be melted, as shown in FlG. 5. Upon the slab 52 there is loaded a supply of material to be melted, as shown at 53 in FIG. 6. This `load may consist entirely of scrap, or it may be scrap mixed with titanium sponge. After the crucible is so loaded and the furnace ev-acuated, the consuinable electrode 5 -is tlOWCI'Cd to the position shown within arcing distance of the scrap 53 and an arc is started, thereby mel ting the scrap, and also melting the electrode 5 gradually. The molten material from the arc fiows down over and melts the unmelted material. Smaller arcs are developed at this time throughout the pile of scrap and sponge which are also effective in melting the material. This phase of the process common-ly proceeds with much turbulence, sputtering and splattering of the molten material. Throughout this phase, the molten material is stirred by the action of the coil 17.

The process just described is capable of melting down titanium scrap in whatever shape or condition it may be, so long as the pieces are small enough to be received in the crucible. Several factors are present which promote the melting action, including: (1) the small local arcs formed between the abutting pieces of scrap; (2) the major arc formed between the consumable electrode and the pile of scrap; and (3) the molten material flowing from the major arc down over the other pieces. While the melting may be successfully accomplished without the use of the stirring coil, it has been found that the stirring coil speeds the melting process considerably.

All of the material supplied to the crucible eventually is melted and most of it solidifies again as a 'solid body of titanium, shown in FG. 7 at 54, having a small molten pool of titauium 55 in its upper surface. After this condition is reached, the consumable electrode 5 is withdrawn, and the nonconsumablc electrodes 28 are lowered so that their tips 29 are adjacent the surface of the pool. Arcs are struck at those electrodes and are supplied with electrical enengy sulficient to rmelt a substantial portion of the titanium in the crcible, lowering the liquid-solid interface to the line indicatecl at *56 in FIG. 8 which, at the center, is close to the position of the upper surface of the original slab 52 of FIG. 5. The temperature maintained in the pocl 55 and the thickness of the solid ti tanium body 54 may be controlled by regulating the heat supplied by controlling the amount of power supplied through the electrode tips 29, and regulating the heat los-s by controlling the flow of coolant through the cooling jackets and 16. After a desired Volume of titanium has been brought to the liquid condition in the pool 55 and ra'sed to a suitable degree of superheat, the three eleotrodes 29 are withdrawn, and the 'auxiliary electrode 34 is lowered -adjacent the pouring spout of the crucible to melt away the soiid material which may be clogging that spout, as shown in FIG. 9. 'If desired, the auxiliary electrode 34 may be brought into action before the electrodes 29 are withdrawn. During all the foregoing operation, current is maintained flowing in the stiring coil 17 to keep the pool agitated so that the composition of the pool is homogeneous. After the material near the pouring `spout has been melted, the crucible is tilted by suitable mechanism included in the supporting frame 19, and not shown in the drawing, so that the pool 55 is poured into the mold dil, as shown in FIG. 10. After the pouring is completed, the material in the crucible M- has the structure shown in FIG. 11. The titanium body 54 in the crucible roughly conforms to the internal contour of the crucible, and is known as a skull? 'It is allowed to remain in that contour and subsequent loads of ma- -terial are deposited within the skull 54, rather than on a slab such as shown at 52 in FIG. 5.

FIGS. 12 to 26 There is shown in these figures a modified form of furnace einbodying the apparatus of the present invention, and with which the process of the invention may be practiced. This furnace is genenally hdicated 'by the reference numezal 6%, and compiises a large generally cylindrical enclosure or tank 61 having `a crucible access opening 62 at the left hand side as viewed in FIG. 12, and a mo-ld :access opening '63 at the rear, as viewed in the same figure. Both openin-gs are closed by suitable covers 62a and 63a. The enclosure 61 rests on legs 64 and is preferably provided with cooling and strengthening fins, one of which is shown in FlG. 12 at olla. The others have been omitted to simplify the drawing. On the top of the enclosure 61 there is provided a central cylindrical extension 65. Projecting up wardly from the top of the extension 65 is a cent al electrode tube 65, which encloses a consumable electrode 57, which may be generally the same as the electrode of FIG. 1. The meohanism for supporting the electrode `67 within the tube 66 may be the same as that shown and claimed in the copending application of Robert J. Ga' my, Serial No. 698256, filed November 22, 1957, now P atent No. 2,973,452. This apparatus -Will be described only briefly herein. 'lt comprises a platform 68 horizontally movable along rails 69 by means of a motor 7%. A pair of masts '71 extend upwardly from the platform :and are ioined at their upper ends by a crossbar 72. A cross-head 73 is guided for vertical movement along the masts 71, and is moved vertical ly by `a pair of concurrently driven lead screws 7 4. The lead screws 74- are driven by a motor 7 5 mounted on the platform 68. A power tube 76 is attached at its upper end to the cross-head 73. The power tube 76 extends through a suitable seal in a cover (not shown) for the upper end of the electrode tube 66, and supports the electrode 67 within the tube by means of a suitable clam-p, which may be the clamp shown and described in the copending application Arthur F. Jones and Donald A. Rice, Serial No. 697702, filed November 20, 1957, now Patent No. 2964580.

The platform 68 and the apparatus mounted thereon are shiftable from the positions shown in the drawing, which are their positions during furnace operation, to positions shifted somewhat to the left as viewed in FIG. 12, which positions are .utilized during 'loading of a new oonsumable electrode into the furnace.

Also projecting upwardly from the top of the extension 65 are three oircumferentially spaced electrode tubes 77, somewhat smaller in diameter than the central electro de tube 66. The tubes 77 enclose non-consurnable electrodes 78 and are provided `at their upper ends with seals so that the electrodes 78 may slide in and out. Each electrode 78 is driven by a lead screw 79, which is in turn driven by a motor 3@ mounted on a fixed platform 81 (FIGS. 12. and 16) just below the furnace Operating position of the movable platform; 68. each electrode 78 istprovided with a tip 159 (FIG. Columns 7811 extend alongside the electrodes 73 and lead screws 79. These colunms serve as supports for limit switches 7% which cooperate in contr'olling the lead screws 79. Theelectrode 78 and tip 1159 are made hollow The lower end of for the purpose of feeding inert gas to the vicinity of the abc when the electrode is being used, in a manner similar to the electro'des 28 of FIGS. 1 to 4. The details of construction of electrodes 78 are described below in connection with FIGS. 23 :and 24.

Inside the enclosure 61, as best seen in FIGS. 14 and 15, a crucible `assembly 82 is mounted on a carriage frame 83 having wheels 84, 8451 by which it is movable along rails 85 which are `aligned with the crucible access port 62 and the cover 62a.

FIGS. 17 to 'The crucible assembly 82 includes a generally cupshaped crucible shell 86, preferably formed of Copper or other material having high ele ctrical conductivity and thermal conductivity. The cruci -le shell 86 is generaly cupshaped and has fastened to the outer edge of its periphery a 'rim 88, preferably .of steel, shown as having a right angle cross-section. The horizont-any projecting flange of the rim 83 is fastened by suitable means to the horizontal flange of an angle section ring 89, also preferably of steel, whose vertical flange is attached to a hoop 99, also preferably of steel, and having a channelshaperd cross-section. One side of the lower flange of the hoop 99` rests ona be-am 91 which is attached at its ends to trunions 92 rotating in trunnion bloc ks %supported by means of plates 94 and 95 on the ca rriage fr aine 83. A portion of the crucible shell 86 and `an aligned portion of the loop 9@ are cut away and a pou'ing spout 96 is inserted in these cut aw-ay portions. The pouring spout 96 may be of gr aphite or other ref ractory material which -'s not attacked by the material being poni-ed.

Projecting laterally from opposite sides of the ring 90 are a pair of pivot pins 97. Each pivot pin 97 is supported on one end of a telescoped cylinder 9311, 98b. The cylinders %a and %b serve as jacks for liftinag the crucible assembly 82 and tilting it about the trunnions 92 so as to pour molten material from the crucible shell 86 through the spout 96 into a mold 99 (see FIG. 15), 'which may be positioned beneath that spout. The crucible assembly 82,7which includes crucible shell 86, ring 96, and associated parts is supported entirely by the bea-m ,91 and the j-aok cylinders 9811, 931).

The axis about which the crucible -assembly tilts (i.e., the axis of trunnions 92) is located close to the pouring spout 96, so that there is -a minimum change in position of the pouring stream as the crucible assembly is tilted between its full and empty positions.

The cylinders %b `are provided with bevel gears me which cooperate with bevel gears 191 fixed on a shaft 102. The shaft 1%2 may be driven from outside the encl'osure 61 by means of' a motor 103 which drives a shaft 164- (see FIG. 14) which extends through a suitable seal in the enclosure Gli and through a slip friction clutch 105 to the shaft 162. Rotation of the bevel gears ll turns the cylinders %b and thereby operates suitable mech- V anism, eg., 'cooperating threads on the cylinders 9851, 931

'to control the expansion 'and contraction of those cylinders.

The electric current for the arcs within the crucible assembly 32fiows from -the arcs` through a metal skull and the crucible shell 86 and thence through a block 106 welded on the bottom of shell 86 and connected through a bus bar 197 to switch fingers 103. The complete circuits for the -arc currents are described below in connection with PIG. 26.

The outside surface of the crucible shell 86 has mounted thereon a cooling coil 109 formed of tubes or pipes,

through which a liquid coolant, e;g., water, -is 'circulated The co'olant is elTect-ive during operation of the furnace to freeze the material ne-arest the wall of the crucible shell 82 land thereby to form the skull 110 inside the crucible, similar to the skull 54 as described 'above in connection with FIGS. l to 11.

A stirring coil generally indicated by the reference numeral 111 is provided for the crucble 82. As best seen in FIG. 17, the coil 111 comprises a series of turns which are clamped between bars 112 mounted on the outside of the crucible 32 by means of beams 113. The coil 111 is preferably constructed of tubing of electrically conductive material, such as copper, through which cool ant is pumped to keep the tubing at a satisfactory Operating temperature.

Current tor -the coil 111 and water for the coils 1119 and 111 are transmitted from outside the enclosure 61 through -a coupling assernbly generally indicate-d at 114. Any suitable coupling arrangements for carrying electric currents and liquids through a wall subject to a pressure differential may be used. The flow diagram of the coolant and the circuit for the electric current in coil 111 are described below in connection with FIG. 25.

The tilting movements of the crucible assembly 82 are controlled in part by limit switches 115, 116 (see FIG. 20), which ane operated by an arm 117 fixed on one of t the trunnions 92. The wires from the limit switches 115 and 116 extend through a Connector diagrammatically indicated at 118 (FIG. 17) and .a cable 119` to the outside of the enclosure 61.

At the inner :end of the rail 35 (the leit hand end in FIG. 17), the-re is provided a stopping block 120* on which is provided a latch arm 121 which may be 'operated by a crank 122, and is provided `at its end with a book for engaging .an aXle 123 on the crucible assembly carriage. After the carriage with the crucible assembly is inserted in the enclosure 61 and the latc'h arm 121 is in `pl-ace as shown in FIG. 17, the carriage is 'held in position and cannot move. Note that the wheels 84 at the side of 'the carrage under the bean 91 are provided with grooves which ride along corresponding ridges on their associated rails 85. At the opposite side of :the carriage, the wheels `8411 `'have cylindrical peripheries and ride along on flat rails 35c. The use of the cylindrical wheels 8451 allows the expansion and contnaction of the carriage which may be necessary because of the wide range of ternperatures encountered within the enc'losure 61, while the grooved w heels 84 and ridged rails 85 guide the assembly against lateral movement.

The crucible assembly 82 is filled with material to be 'melted by simply running the cruci-ble outside the enclosure 6'1 :and filling it by means of a cr-ane orotherw-ise. Some of the material melted is supplied by the consumable electrode 67. The operating process generally foliows that illustrated in FIGS. to l l above.

FIGS. 21 and 22 A crucible cover or shield 124 is provided, as shown in FIGS. 21 and 22. The shield 124 is supported on three radially extending arms '125 whose outer ends are attached to the lower end of vertical' rods 125 which eX- tend upwardly through suitable scaling members 127 into tubes 128 mounted on the upper side of the enclosure 61. A lead screw 129 extends downwardly through the center of each tube 128 and operatively engages the upper end 'of the rod 126. Each lead screw 129 is driven by a motor 1311, mounted on the upper end of tube 128. The three motors 130 are operated concurrently so as to raise and lower the s'hield 124. The shield 124 is lowered whenever an are is present inside the crucible 82, to conserve heat within the c-rucib le.

FIGS. 23 and 24 These figures illustrate the details of Construction of one of the non-consumable electrodes 7 8. Each eleotrode 78 comprises an upper couplng member 131, a lower coupling member 132, -an outer power supply tube or cylindet 133, an inner power 'supply tube or cylnder 134, and an electrode tip 159. The coupling members are preferablymade of copperas is the cylinder 134. The cy-linder 133 is preferably stainless steel, and the parts are brazed together. The electrode rtip 159 is preferably of graphite and is drilled to provide pass nge s and 15% for a flow of cooling inert gas, for example, argon or thelium. The passage 15911 communioates with a drilled passage 132a 'in the lower coupling member 132. The other end of passage 1.32@ receives one end of a copper tube 135 which extends through :the electrode and through the upper coupling member 131. Its upper end is connected to any suitable source of inert gas.

A nut 1,36 having a flange 136a is attached to the upper surface of the upper coupling member 131. The nut 136 is internally threaded and cooperates with a lead screw 137 extending .through the center of the electrode to drive the electrode up and down. The `lower end of the lead screw 137 is provided with a ball bearing138 to minimize any frietion there may be between it and the inside of the cylinder 134, A plurality of water inlet passages 131a are drilled into the upper coupling member 131. A similar plurality of water conduts 139 are located within the space between the cylinders 133 and 134 and convey cooling water fromthe inlets to the bottom of that space, the lower end of the water pipes 139` being spaced above the bottom coupling member 132. A similar plurality 'of water outlets 131b are drilled into the upper coupling member 131 and communicate with the space between the cylinders 133 and 134. The inlets and outlets are connected to any suitable Water supply couplings. These couplings and the gas supply coupling hold the electrode against rotation when it is being 'dmiven up or down by the lead screw 137.

The parallel power supply tubes 133 and 134 Carry the electrode current. The current may -be supplied to the electro des through any suitable connector mechanism (not shown).

FlG. 25

This figure shows diagrammat-ically the water circulation and electr-icai supply connections 'for the stirring coil 111 and for the cooling coil 10 9, which coils are shown in greater detal in FIG. 17. The stirrirg coil 111 is formed of Copper tubing.. While .its primary function is to carry direct current, water is circulated through the tubing for the purpose Gif keeping it at a temperature Where it will not lose its strength. A common water supply is used for both the stirring coil and the cooling coil 1119 The cooling coil 1119 is necessarily electricatly connected to the crucible shell 86 In order to use a common water supply and at the same time transmt an electric current through the stirring coil 111, insulating sections must be used in some of the pipes.

The electric oircuit tor stirring coil 111 may be traced in FIG. 25 from one terminal of a power supply 141! through, a wire 14 1, through a suitable connection to a Water supply pipe 142, which extends by means of a suitable coupling through the wall of tank 61 and thence through a pipe 1 53 to coil 111, and out of the dischargc ppe 144 to the outside of the tank 61 and thence through a suitable coupling to a wire 1425 leading to the opposite terminal of the power supply.

The rwater supply for stirring coil 111 may be traced from a suitable inlet 146, an insulating pipe section 147, pipes 142 and 143, coil 111, pipe 144, and insulating pipe section 148 to a discharge outlet 149.

The cooling coil 10 9' is sectionalized for purposes of water circulation into six sections 18 961, 10917, 111%, 10%, 11196 and 10 91. The sections 10% and 16% are connected in parailel and serve a zone at the upper part of the crucibie shell 86. The coils 11190 and 111% are likewise in parallel and serve a zone near the central portion of the shell 86. The coils 1119@ and 161# are in parallel and serve a zone at the bottom of the shell 86. The water supply [for the three pairs of cooling coils may be traced in PTG. 25 from the iniet 146 through an insulating pipe section 147, through a T-connection into a pipe 15@ :which passes through the wall of the tank 61 at a suitable coupling, an insulating pipe section 151, and a manifold 152 which leads to all the cooling coils in parallel. The respective pairs of cooling coils discharge 

1. A FURNACE FOR MAKING INGOTS OF MELTABLE MATERIAL, COMPRISING A CRUCIBLE TO RECEIVE MATERIAL TO BE MELTED, MEANS FOR CONNECTING SAID CRUCIBLE TO ONE TERMINAL OF A SOURCE OF DIRECT ELECTRICAL ENERGY, A HOLLOW ELECTRODE HAVING A HOLLOW TIP ADAPTED TO COOPERATE WITH THE MATERIAL TO BE MELTED IN THE CRUCIBLE, MEANS FOR MAINTAINING A SUBATMOSPHERIC PRESSURE IN THE FURNACE, AND MEANS FOR 